| and || - what is the difference between these two operators in PHP?
views:
270answers:
6Bitwise or means that the value of (a|b) is the set of bits that are set in either a or b. Logical or means that the value of (a||b) is true if either a or b is true or both or true, false if neither is true.
jeffamaphone
2010-02-10 01:38:19
As a smalll side question, in PHP can you use the bitwise or on booleans like you can in Java and C#? The practical difference in those cases is that the || will perform a shortcut where if the left disjunct returns true, the right is not checked, whereas with the single | it will perform the check in both cases.
Jacob Bellamy
2010-02-10 01:43:24
@Jacob Bellamy : a simple test (`# php -r 'var_dump(true | true);'`) suggests that you can. `bool(true)` is probably being automagically cast to `int(1)`. I'd be a bit hesitant about using that syntax myself, as I wouldn't necessarily expect the other guys I work with to pick up on the subtle difference. Similarly, I'm hesitant to use the `or` operator, which unlike `||`, is lower precedence than assignment.
Frank Farmer
2010-02-10 02:15:41
RTFM isn't really a good stand-alone answer, despite how basic the question might be and how good it might feel.
jeffamaphone
2010-02-10 01:39:17
@jeffamaphone> Just adding links to an already answered question. Perhaps the OP would like to read more on the proper use of operators.
bdl
2010-02-10 01:44:12
A:
| operates on the bits of a variable: 2 | 4 = 6
|| operates on The Boolean value of a variable: 2 || 4 = TRUE
Mike Sherov
2010-02-10 01:39:51
+5
A:
Meaning
| is binary operator, it will binary OR the bits of both the lefthand and righthand values.
|| is a boolean operator, it will short circuit when it encounters 'true' (any non-zero value, this includes non-empty arrays).
Examples
print_r(1 | 2) // 3
print_r(1 || 2) // 1
When used with functions:
function numberOf($val) {
echo "$val, ";
return $val;
}
echo numberOf(1) | numberOf(2); // Will print 1, 2, 3
echo numberOf(1) || numberOf(2); // Will print 1, 1
LiraNuna
2010-02-10 01:41:59
A:
| -> binary operator || -> boolean operator or -> also a boolean operator with lower prescedence
$x = false | true; //will set $x to an integer
$x = false || rue; //will set $x to true
$x = false or true; //will set $x to false exactly the same that:
($x = false) || true;
useless
2010-02-10 03:14:38
A:
Just like the & and && operator, the double Operator is a "short-circuit" operator.
For example:
if(condition1 || condition2 || condition3) If condition1 is true, condition 2 and 3 will NOT be checked.
if(condition1 | condition2 | condition3) This will check conditions 2 and 3, even if 1 is already true. As your conditions can be quite expensive functions, you can get a good
performance boost by using them.
There is one big caveat, NullReferences or similar problems. For example:
if(class != null && class.someVar < 20) If class is null, the if-statement will stop after "class != null" is false. If you only use &, it will try to check class.someVar and you get a
nice NullReferenceException. With the Or-Operator that may not be that much of a trap as it's unlikely that you trigger something bad,
but it's something to keep in mind.
No one ever uses the single & or | operators though, unless you have a design where each condition is a function that HAS the be
executed. Sounds like a design smell, but sometimes (rarely) it's a clean way to do stuff. The & operator does "run these 3 functions,
and if one of them returns false, execute the else block", while the | does "only run the else block if none return false" - can be useful,
but as said, often it's a design smell.